References of "Gaydardzhiev, Stoyan"
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See detailPotential for application of alkali roast acid leach technology for removal of phosphorus from iron ore
Ionkov, Krassimir ULg; Gaydardzhiev, Stoyan ULg; Bastin, David ULg et al

in Proceedings of 6-th International Congress on the Science and Technology of Ironmaking ICSTI (2012, October)

The present study deals with the effect of sodium hydroxide and sodium carbonate used as additives during oxidizing roasting of oolitic limonite iron concentrate and more precisely upon the change in its ... [more ▼]

The present study deals with the effect of sodium hydroxide and sodium carbonate used as additives during oxidizing roasting of oolitic limonite iron concentrate and more precisely upon the change in its magnetic susceptibility. Further, the efficiency of Alkali Roast Acid Leach (ARAL) technology for dephosphorisation of the concentrate is compared with the case when sodium hydroxide was added in alkali leach after roasting. The treatment without additives in roasting resulted in obtaining iron concentrate with 58 % iron and 0.21 % phosphorus, while the ARAL approach yielded concentrate with 63 % iron and 0.09 % phosphorus. The influence of combination of coke as reducing agent and sodium hydroxide in roasting at 900°C is also investigated and results displayed in 3D form. The combination of ARAL with reductive roasting, grinding of the clinker to 80 % - 0,075 mm, flotation of the non-reacted coke and magnetic separation before and after the acid leach resulted in iron concentrate with 66 % iron and 0.05 % phosphorus. The study has shown that the application of the ARAL approach with low addition of alkalis followed by 10 to 15 minute acid leaching at ambient temperature could substantially reduce phosphorus, thus offering the possibility for efficient treatment of high phosphorus iron ores. [less ▲]

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See detailRemoval of phosphorous through roasting of oolitic iron ore with alkaline earth additives
Ionkov, Krassimir ULg; Gaydardzhiev, Stoyan ULg; Bastin, David ULg et al

in Proceedings of the XXVI International Mineral Processing Congress (2012, September)

The present study is devoted to improvement of the leaching efficiency during phosphorous removal from high phosphorous gravity-magnetic concentrate. Before leaching the concentrate has been subjected to ... [more ▼]

The present study is devoted to improvement of the leaching efficiency during phosphorous removal from high phosphorous gravity-magnetic concentrate. Before leaching the concentrate has been subjected to roasting with the addition of either Ca(OH)2 or CaO. The oolitic iron ore is roasted at 900°C for one hour. This reflects in reaction between alkaline earth additive and quartz, aluminosilicates, phosphorus, and some other minor components of the gangue minerals. The application of leaching, physical separation, and wash out of salts has resulted in the decrease of phosphorus from 0.7 to 0.15 % and it is established that the major influencing factor is the concentration of acid and to a less extent duration of the leaching process. About two third of the phosphorus can be removed by roasting with 3 % CaO to hematite, coarse grinding to d50 0.3 mm, dry high intensity magnetic separation and leaching of the magnetic fraction with hydro-chloric or nitric acid. [less ▲]

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See detailInfluence of selected parameters on the flotation of Cu-Mo ore from Ellatzite deposit in Bulgaria
Gaydardzhiev, Stoyan ULg; Bouchat, Harold ULg; Dedelyanova, K et al

in Proceedings of the XXVI International Mineral Processing Congress (2012, September)

Laboratory batch tests having preliminary and orientation character aiming at improvement of the molybdenum flotation at Ellatzite copper processing plant in Bulgaria have been conducted. The following ... [more ▼]

Laboratory batch tests having preliminary and orientation character aiming at improvement of the molybdenum flotation at Ellatzite copper processing plant in Bulgaria have been conducted. The following technological parameters have been screened to study their influence on the grade and recovery of copper and molybdenum during the rougher flotation stage: flotation pulp density, pH, addition of secondary collector and replacement of MIBC by pine oil as a frother. The results have shown that slightly better grade/recovery figures could be obtained for both copper and molybdenum at lower flotation pulp densities. The addition of kerosene has improved the recovery of molybdenum however on the expense of that of copper. The effects from pH variation and the replacement of MIBC by pine oil as a frother have been almost negligible. [less ▲]

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See detailBio hydrometallurgical recovery of metals from Fine Shredder Residues
Lewis, Grégory ULg; Gaydardzhiev, Stoyan ULg; Bareel, Pierre-François et al

in Minerals Engineering (2011), Vol 24, Issue 11

The leaching step of an integrated hydrometallurgical process for the selective recovery of metals from polymetallic concentrates has been investigated. The concentrate has been produced by physical ... [more ▼]

The leaching step of an integrated hydrometallurgical process for the selective recovery of metals from polymetallic concentrates has been investigated. The concentrate has been produced by physical treatment of Fine Shredder Residues derived from a shredding plant processing a mixed feed. Bacterially assisted leaching experiments using a copper-adapted consortium of mesophilic bacterial strains have been carried out. Various technological parameters have been studied. Under optimal conditions about 95 % extraction levels for copper and zinc have been obtained. Bacterial presence has been found beneficial in view catalysing copper dissolution. [less ▲]

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See detailDEPHOSPHORIZATION OF LIMONITIC CONCENTRATE BY ROASTING, ACID LEACHING AND MAGNETIC SEPARATION
Ionkov, Krassimir ULg; Gaydardzhiev, Stoyan ULg; Corea de Araujo, Armando et al

in Holmes, M. (Ed.) Proceedings of the Iron Ore 2011 International Conference (2011, July)

The oolitic iron ore reserves in Lisakovsky, Northwest Kazakhstan represent a quite challenging deposit both from technological and from resource point of view. The difficulties in processing such type of ... [more ▼]

The oolitic iron ore reserves in Lisakovsky, Northwest Kazakhstan represent a quite challenging deposit both from technological and from resource point of view. The difficulties in processing such type of ore are connected with the extremely fine dissemination of phosphorus and gangue minerals inside the oolitic formations. The goethite crystals are cemented in their structure by aluminosilicates with quartz and other gangue minerals and dissemination is so fine that they are not separable by physical methods. The laboratory tests performed in direction of dephosphorisation have shown that the combination of alkaline roasting followed by low intensity magnetic separation and acid leaching enables the obtaining of high grade iron concentrate. The magnetic separation performed ahead of leaching has been efficient by means of buffering the high pH via washing out the soluble salts and the excess of bases and applied after leaching has facilitated the removal of secondary liberated gangue minerals in the non-magnetic fraction. As a consequence, phosphorous content has been dropped to a more acceptable for the ferrous metallurgy levels while iron grade and recovery have reached respectively 61.6 and 80.8 percent. [less ▲]

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See detailCopper extraction from scrap cables by biotechnological means
Gaydardzhiev, Stoyan ULg; Bastin, David ULg; Bareel, Pierre-François

in Proceedings of the XXV International Mineral Processing Congress (2010, September)

The papaer reports on laboratory results regarding bio leaching of metallic copper from cable-bearing scraps derived from recycling of end-of-life vehicles. The copper has been met in pure form as ... [more ▼]

The papaer reports on laboratory results regarding bio leaching of metallic copper from cable-bearing scraps derived from recycling of end-of-life vehicles. The copper has been met in pure form as irregular shaped wires often coated with tin. The complex nature of the material renders both gravity and physicochemical separation unsuitable for efficient copper separation. Hence a bacterially assisted leaching with mixed consortium of mesophylic microorganisms has been tested for recevery of the remaining copper. Continuous adaptation of the cultures to the substrate has been envisaged in order to guarantee sufficient degree of ferric iron regeneration by bacteria during leaching. It has been established that under optimal leaching conditions such as acid consumption, pulp density, pH and temperature, it is possible to recover nearly 98 % of the copper in solution within acceptable leaching duration. [less ▲]

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See detailBiosolubilization of copper from waste electric cables
Gaydardzhiev, Stoyan ULg; Bastin, David ULg; Goffinet, Florence ULg et al

in Harre, Jens (Ed.) Proceedings of the Copper 2010 International Conference (2010, June)

The paper reports on results from a laboratory tests for bacterial leaching of copper from scrap cables. The studied material is a reject fraction obtained after dismantling and separation of electric ... [more ▼]

The paper reports on results from a laboratory tests for bacterial leaching of copper from scrap cables. The studied material is a reject fraction obtained after dismantling and separation of electric cables during recycling of end-of-life vehicles (ELV). The copper has been met predominately in pure metallic form as tiny irregular shaped wires often coated with tin and well liberated from the plastic isolations. For bringing copper in solution, a bacterially assisted agitative leaching with mixed consortium of mesophylic microorganisms has been chosen. Continuous bacterial adaptation of the cultures to the substrate has been envisaged in order to provide an efficient way for ferrous iron regeneration during the leaching. It has been established that under optimal conditions of pH, density and temperature it is possible to recover nearly the total copper within short leach duration. The obtained pregnant leach solution could be subjected to subsequent copper recovery via solvent extraction, while the solid leached residue could be considered as non-metallic material containing plastics suitable for recycling. [less ▲]

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See detailSeparation of Copper and Zinc by Solvent Extraction During Reprocessing of Flotation Tailings
Kitobo, Willy; Gaydardzhiev, Stoyan ULg; Frenay, Jean ULg et al

in Separation Science & Technology (2010), 45(4), 1-6

Results from solvent extraction of copper and zinc from pregnant solutions after bioleaching of re-floated tailings from the Kipushi concentrator in DR of Congo are presented. LIX984N has been used as ... [more ▼]

Results from solvent extraction of copper and zinc from pregnant solutions after bioleaching of re-floated tailings from the Kipushi concentrator in DR of Congo are presented. LIX984N has been used as extractant for copper, while D2EHPA as such for zinc, following prior removal of the ferric iron via precipitation. The McCabe-Thiele diagrams constructed for Cu and Zn extraction have theoretically suggested the need for two stages for copper and one for zinc. Stripping these metals to aqueous phase by sulphuric acid has yielded rich electrolytes with 48.5 g/L copper and 85.5 g/L zinc. Thus, copper and zinc could be further recovered from the stripped solutions by electrolysis. [less ▲]

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See detailGetting more out of end-of-life vehicles – a bio hydrometallurgical approach
Lewis, Gregory; Bastin, David ULg; Gaydardzhiev, Stoyan ULg et al

Conference (2010)

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See detailImproving the grinding performance in ball mills with a conductive and inductive sensor
Köttgen, Axel ULg; de Haas, Bernard; Keshav, Pratish et al

Poster (2010)

A series of tests were conducted in a South African concentrator on the secondary grinding mill. The results were analysed and provided showed the importance of selecting an optimum density and filling ... [more ▼]

A series of tests were conducted in a South African concentrator on the secondary grinding mill. The results were analysed and provided showed the importance of selecting an optimum density and filling degree of the mill. Moreover, a Sensomag (r) is installed on this mill and the surveys showed that an increase of the density was improving the mixing of balls in the pulp and increasing the grinding performance. [less ▲]

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See detailBacterial leaching of complex sulphides from mine tailings altered by acid drainage
Kitobo, Willy; Gaydardzhiev, Stoyan ULg; Frenay, Jean ULg et al

in Dominic, Esteban (Ed.) Bacterial leaching of complex sulphides from mine tailings altered by acid drainage (2009, May)

An experimental study aimed at re-flotation of laid down tailings from Kipushi (DRC) to bring sulphide concentrate suitable for further processing by hydrometallurgical means has been realized. The ... [more ▼]

An experimental study aimed at re-flotation of laid down tailings from Kipushi (DRC) to bring sulphide concentrate suitable for further processing by hydrometallurgical means has been realized. The results from a bioleaching route chosen to accomplish the later task by use of moderate thermophilic and mesophilic microorganisms are reported. It has been found that due to the complexity of the treated material, the leaching pattern of the two principal metals of interest, copper and zinc vary. Whilst the copper bearing minerals have been leached relatively fast by direct mechanism, the leaching kinetics for the zinc minerals has been moderate involving predominantly an indirect mechanism. The effects of pH and temperature variations and ferrous ions addition upon the extent of copper and zinc dissolution have been examined. The presence of ferrous ions has been found beneficial for the leaching of sphalerite, however the concomitant formation of jarosite precipitates has led to copper leaching hindrance. Similarly, the rapid zinc solubilisation has been counterbalanced by decrease in rate of copper dissolution. [less ▲]

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See detailFibrous natural materials for ceramic processing
Gaydardzhiev, Stoyan ULg; Wilker, Viola; Scheffler, Michael

in Zuo, Wang (Ed.) Proceedings of the XXIV International Mineral Processing Congress (2008, September)

Initial experiments towards preparation of hollow ceramic microtubes by dip-coating of fibrous plants with water based alumina gel-casting slurries using hemp and coconut fibres as templates have been ... [more ▼]

Initial experiments towards preparation of hollow ceramic microtubes by dip-coating of fibrous plants with water based alumina gel-casting slurries using hemp and coconut fibres as templates have been done. It has been found that the wettability of fibres and accordingly the stability of the developed ceramic layer on their surface during slurry gelation varied significantly within the different fibre types. Good correlation between the diameters of the template fibres and the resulting channels has been found at the 31 % solids loadings level. Hemp fibres used as bundles have led to formation of multi channel patterns while the coconut fibres-templated process resulted in uniform monochannel materials. The micro tubes have shown good mechanical handling properties. [less ▲]

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See detailDip-coating of fibrous natural materials for alumina tube manufacturing
Gaydardzhiev, Stoyan ULg; Wilker, Viola; Scheffler, Michael

in Advanced Engineering Materials (2008), 10(3), 223-226

Results from preliminary studies for development of hollow ceramic tubes by dip-coating of fibrous plants with water based gel-casting slurries are presented. Hemp and coconut fibres have been tested as ... [more ▼]

Results from preliminary studies for development of hollow ceramic tubes by dip-coating of fibrous plants with water based gel-casting slurries are presented. Hemp and coconut fibres have been tested as templates reflecting in different macro and micro structures of the obtained ceramic tubes. Good correlation between the diameters of the template fibres and the developed channels has been documented, the ordering of the channels inside the tubes being function of the mode of fibres implementation: as singles or as bundles. By coating hemp fibres in bundle, multi channel pattern has been developed, resulting from splitting of the bundle. By using single coconut fibre as template, uniform mono channels with 250 – 400 µm in diameter were observed. The developed tubes have been characterized by good end finish. The observed differences in their microstructure offer possibilities for adjusting the physical properties towards prospective application niches. [less ▲]

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See detailGel-casted porous Al2O3 ceramics by use of natural fibres as pore developers
Gaydardzhiev, Stoyan ULg; Gusovius, Hans; Wilker, Viola et al

in Journal of Porous Materials (2007)

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See detailCharacterisation of stability behaviour of ultra fine alumina powder in view its colloidal processing by gel-casting
Gaydardzhiev, Stoyan ULg; Ay, P.

in Onal G. et al. (Ed.) Proceedings of XXIII International Mineral Processing Congress, 3-8 September 2006, Istanbul (2006, September)

The paper reports on results study aimed at assessing of the influence of dispersant type on the electrochemical properties of highly concentrated alumina suspension. The relationship between the type of ... [more ▼]

The paper reports on results study aimed at assessing of the influence of dispersant type on the electrochemical properties of highly concentrated alumina suspension. The relationship between the type of dispersant and the stabilization ability towards ultrafine alumina powder CT3000 has been studied. The effectiveness was determined mainly by the zeta potential value, specific surface charge, the shift in the pH(iep) and by visual controlling the fluidity of the slurry at constant solid loading. A good agreement between the zeta potential and the specific surface charge as a way to determine the optimal dose of dispersant has been documented. Gel-casting experiments showed that the Dolapix CE64, an ammonium polyacrylate dispersant was the best dispersant for the studied powder. [less ▲]

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See detailRemoval of selected azo dyes from textile wastewater by chemical coagulation/flocculation: implication of the dye destabilization mechanism
Janeczko, M.; Gaydardzhiev, Stoyan ULg; Ay, P.

in Fecko P et al. (Ed.) Proceedings of 10-th Conference on Environment and Mineral Processing (2006, June)

The results of the coagulation/flocculation of six commercially used textile azo dyes coagulated with synthetic primary coagulants are discussed in the paper. Surface charge measurement of coagulated dye ... [more ▼]

The results of the coagulation/flocculation of six commercially used textile azo dyes coagulated with synthetic primary coagulants are discussed in the paper. Surface charge measurement of coagulated dye-flocs was employed to find a correlation between its sign and the level of colour removal. Additionally, flocs characterization was done with the aim to link data with surface charge and on this basis to outline the predominant mechanism of colour removal. Based on the results obtained, the evident correlation between surface charge density progression of coagulated dye flocs and colour removal after different solid/liquid separation methods was observed. Thus, it was concluded that the charge neutralization was the predominant mechanism responsible for dye destabilisation. It was found out also that flocs produced at optimal dosage are characterized by large median size and high value of fractal dimension [less ▲]

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See detailRemoval of dyes from textile wastewater by chemical coagulation
Janezcko, Marta; Gaydardzhiev, Stoyan ULg

in Önal, G. (Ed.) XXIII International Mineral Processing Congress, 3-8 September 2006, Istanbul (2006)

Dye removal mechanisms from textile effluents has been studied by means of surface charge measurempents and image analysis of floc sludge (size, shape, sedimentation properties). Reactive Black 5 and Acid ... [more ▼]

Dye removal mechanisms from textile effluents has been studied by means of surface charge measurempents and image analysis of floc sludge (size, shape, sedimentation properties). Reactive Black 5 and Acid Black 1 commercial dyes have been tested as simulated effluent water solutions treated with synthetic primary coagulants. [less ▲]

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